FOR MUCH OF his life, Matthew Roberts has suffered from night terrors. They’re dreams, yes, but they’re a lot more vivid than the usual REM-sleep brain tangents, and they often take him to the brink of what he describes as “an emotion beyond fear or horror.” He might be sitting in bed with his eyes wide open, but a few feet away he’ll see a cluster of aliens torturing human beings—melting their skin as if it were under a magnifying glass. “Sometimes I wake up covered in spiders,” he says. “Just hellish stuff. Movie-nightmare stuff. Some of it I won’t even tell you, I won’t even describe.”

As Roberts (see photo) says this, he is wearing a black suit and sitting with a kind of magisterial stillness in a red leather banquette at a strip joint in Van Nuys, Calif. People often feel as though they’ve met Matthew Roberts before: His face is bracingly familiar in a way that makes you unsure of whether to stare or turn away. An aspiring singer, songwriter, and author, he works here at Rouge a few days a week as a DJ, pumping up the soundtrack for scantily clad dancers when they make a beeline for the pole or a waiting lap. It’s a slow Sunday morning, though, so while everyone prepares for the first customer of the day, Roberts takes a moment to sip a soda and explain why he feels, at times, like Rosemary’s baby.

He has come to this sensation by degrees. He was born in Chicago in March 1968 and adopted a few days later by a quiet, straight-laced couple from Rockford, Ill. His childhood was placidly Midwestern—well, except for those night terrors. He played football. He banged the skins in a garage band. He went to church and pledged his soul to the Lord. But after graduating from high school, he found himself drawn to rock and roll and the West. He moved to Los Angeles, enrolled in the Musicians Institute in Hollywood, met and became temporarily engaged to a woman named Gina, and gradually—at Gina’s urging—got to wondering who his biological parents were.

Roberts pursued the mystery, but very slowly—the L.A. move came in 1986, but he didn’t start digging into his genetic roots for a decade. First he found his biological mother. In 1999 he called an adoption-search organization in the Midwest, coughed up a few hundred dollars, and was given her name. She was living in a cabin in Wisconsin without a phone or a car, he says. “The adoption lady kind of warned me, ‘Your mother’s a little bit off.’ Then I got a letter from my mother, and she was talking about her rhubarb and her cats, and I thought, Well, she’s just kind of a hippie. But at a certain point it became obvious that there was something wrong with her. Mentally.” The woman, a Wisconsin native whom he calls Terry, said that his first and middle names at birth had been Lawrence Alexander. According to Roberts, she sent him food in the mail after warning him, in a weirdly winking way, that her own mother had suffered from Munchausen syndrome, a mental disorder that can lead parents to poison their children. “One time she sent me a jar of, like, mystery juice,” Roberts says. “It had things floating in it. Then she asked me, ‘Did you drink the juice?’ And I said, ‘No.’ And she said, ‘You’re smart!’”

Roberts was beginning to get a sense of where those night terrors might have come from. Only gradually, he says, did his mother let the narrative wrinkles slip out: that he had been conceived during a hippie orgy in San Francisco in 1967, that his mother’s participation in the orgy may not have been consensual, that there were four men present, that everyone at the orgy was dropping LSD, that his mother had apparently continued to ingest LSD in the months that followed. It was all eerily similar to Rosemary’s Baby: Midway through Roman Polanski’s 1968 film about the prenatal care and feeding of Satan’s spawn, Ruth Gordon coaxes a pregnant Mia Farrow into gulping down a frothy, fetid glass of herbal goop. In the movie, Roberts says, “they were doing it to create an Antichrist. Well, in this case it just happened.” That was a safe assumption, of course, until the day in 1999 that Matthew Roberts finally sent his biological mother a photo of himself, at about 30 years old, with his piercing eyes and his tangled nest of black hair, and she told him she realized which of the four men at the orgy had to be his father: Inmate No. B-33920 at the California State Prison in Corcoran, otherwise known as Charles Manson, the most demonic figure in the annals of American murder.

IT’S DECEMBER 2009. Forty years after the city of Los Angeles marinated in its own collective night terror in the wake of the Manson Family’s grisly killing spree, Roberts cups a microphone in his hands on stage at the Cat Club, a rock-and-roll boîte on the Sunset Strip, and launches into a driving industrial-goth anthem that has the same name as his band: “New Rising Son.” He’s about a foot taller than the founder of Helter Skelter Inc., but he seems to share Charlie Manson’s talent for transfixing a crowd. The chorus of the song, in part, goes like this: “Dad you are my motherf---er funky chicken space brother / Did you ever love my mother? / I guess about as much as I loved you.” (He says later: “I’m pretty proud of those lyrics.”)

When Roberts first heard from his mother about the alleged Manson connection, he was disinclined to believe it, although he wanted to know more. When he started asking questions, he says, she became hostile, so he dropped the subject. He became convinced that he was Manson’s flesh and blood only later, in 2002, after he started writing letters to Manson in prison. Manson responded quickly—in a week or two—and his nearly indecipherable chicken-scratch missives contained details that, according to Roberts, suggested that Manson had been present at the orgy. Manson referred to him as Lawrence Alexander. He also mentioned a story that Roberts had heard from his mother about a day in 1967 when her father had chased Manson off his property and called the future cult leader a “white-trash biker bandit.”

When that first letter from Manson arrived, Roberts was living with a band mate, bass player John Eckert, a short dash from the Spahn Ranch, the exurban enclave that had served as the Manson Family’s headquarters in the late ’60s. “That blew my mind,” Roberts says. “Here I am, right near where all that stuff took place. Here I am, playing in a band, dating strippers, conspiring to take over the world, and I’m like, ‘Oh, my God. Do I have any free will at all?’ You know, I’m, like, following in this guy’s footsteps completely! That really freaked me out. I was in a spot where you can’t really tell anyone because you’re gonna look like a crazy person.”

“You could see that he was going through some kind of identity crisis,” recalls Eckert, who runs a medical-marijuana dispensary in the San Fernando Valley. “He was unsettled. He was confused. He came in and said, ‘Check this out, I got a letter from Charlie Manson, bro.’ Here you are, hanging out with this guy, and suddenly there’s a strong possibility that he’s Charlie Manson’s son. I mean, how do you take something like that?” For his part, Eckert was uneasy—among his concerns was the shroud of darkness the news cast over New Rising Son. “If we stand on the quality of our songs alone, we’re a good band,” he says. “We might’ve done better without the Manson thing. It’s a negative for a lot of people. They don’t take you seriously.”

OF COURSE, IF you or I were to discover that the leader of a messianic thrill-kill cult may have been the source of half of our DNA, our first impulse might be to prove, using every conceivable scrap of evidence, that we are nothing like him. And to be fair, Roberts does take pains to point out that he is a gentle, contemplative soul who’s been known to stand at the rim of a swimming pool scooping out drowning bugs with a cup. He is also a devout vegetarian—“I just don’t like killing things,” he says. (Then again, Manson was a vegetarian too.) But there have been times when the echoes between Roberts’ life and Manson’s have been so striking—so weird—that he’s begun to wonder whether he’s receiving signals from the universe. After all, “mass-murdering mystic” was Charlie’s backup plan; his original career goal was “rock star.”

The First Rays of the New Rising Sun, a 157-page memoir-manifesto that Roberts says he wrote in his 20s, is rife with Mansonisms. Full of ruminations on dozens of quasi-scientific-spiritual topics and studded with lines like “Oxygen will fire the codes of consciousness,” the tome comes across as something that Manson himself might’ve dictated to a harem of stoned flower children while cruising through Death Valley in a dune buggy. “I know, I know,” Roberts says. “Stuff in that book is a page out of his rhetoric. And I wrote it when I was 23 years old. It just came to me, like music does.”

Roberts is inclined to attribute any creepy parallels to “morphic resonance” or “quantum entanglement.” A more hardened soul might be led to wonder whether he’s just making things up. Roberts hasn’t gone through a DNA test with Manson yet—getting reliable genetic data from a convicted felon turns out to be more of a challenge than you might imagine—and he firmly resists letting the press contact his adoptive family or his biological mother. But if Roberts’ biological mother didn’t at least suspect that Manson had fathered the baby she delivered in Chicago in 1968, how did Manson learn of the name Lawrence Alexander?

Whatever the answer, there’s no denying that Matthew Roberts is an ambitious fellow. He wants to develop a “son of Manson” reality show with a production company in Orlando and counts among his close advisors Vicky Hamilton, a savvy West Coast music-biz fixture who helped break bands like Guns N’ Roses and Poison. A few years ago Roberts auditioned for the guitarist Slash in a bid to become the singer for the band Velvet Revolver. “I’ve been in seclusion for long enough,” he says. “Superstardom would be kind of cool.”

Could the whole saga be a stunt to draw attention to his music? “I’ve been accused of trying to promote my band,” Roberts says. “But I’ve never made one phone call. People call me.” Still, he understands why some are skeptical. He, too, doubted the story early on. “I kind of kept it to myself, because I really didn’t expect anyone to believe it,” he says. “I mean, it just seems so ridiculous.”

Strangely enough, if Roberts’ story is ever confirmed, the proof will likely come from Charles Manson himself—a DNA sample or a scrap of info that unlocks the mystery. Sitting outside a cafe in downtown Los Angeles, Roberts reaches into a sheaf of letters that he’s received from Manson. He selects a piece of lined paper and reads the jagged scrawl aloud. “‘You never heard the song I did for you before you were born.’” Roberts begins to recite the lyrics—I’ll never say never to always / It’s inside yourself for your father / I will find you somewhere on a sunshine beam—and as he does, the experience seems to bring him to an odd kind of reverie. “This is a beautiful song,” he says. “It’s really nice poetry. And this to me shows some real, you know, love.”

Therein lies a conundrum: If Charlie Manson is your dad, are you supposed to love him? “I feel empathy for him,” Roberts muses. “And that’s very similar to love, in my world. But I don’t necessarily need him to love me. I just accept it. It wasn’t like I was loved and then my parents took their love away from me. When I came to know them, they were unlovable.”

From a story by Jeff Gordinier that originally appeared in Details. ©2010 by Condé Nast. Reprinted with permission. All rights reserved